This invention relates to the weft inserting mechanism of a vertical weaving machine. In particular, the invention concerns limiting the divergence of the weft-yarn-carrying heads of the entry and exit rapiers when they come together for yarn transfer during the weft insertion operation.
The rapiers in a weaving machine are typically composed of an elongated tubular section having a thread carrying head which travels into and out of the warp shed during the weft inserting operation. Depending on the amount of support provided along the length of the rapier, the rapier head experiences varying degrees of random movements in combinations of horizontal and vertical directions transverse to the longitudinal movement of the rapier while the rapier is traveling in the warp shed. In standard looms having a generally horizontal configuration the rapiers are supported along their entire length during the weft inserting operation since they rest on a warp sheet supported by the lay of the machine while traveling in the shed. The situation is considerably different in weaving machines having a vertical configuration such as those currently being developed for weaving triaxial fabric of the type disclosed in U.S. Reissue Pat. No. Re. 28,155 and U.S. Pat. No. 3,874,422 both issued to Norris F. Dow. Weaving machines constructed with a vertical configuration do not readily lend themselves to providing mechanical supports for the rapiers as is done in standard horizontal looms. In vertical weaving machines the rapiers are cantilevered in such fashion that the weft carrying head is susceptible to random transverse movement while traveling in the shed. In order to attain successful transfer of the weft yarn from the entry rapier to the exit rapier it is essential that the rapiers come precisely together. The inherent instability of the cantilevered rapiers can result in misalignment of the rapiers at the weft transfer point and consequently the exit rapier fails to grip the weft yarn. This results in a flaw in the fabric. When there is a missed transfer the machine is stopped by a stop motion device and the weft yarn must then be inserted manually. To obtain high efficiency the number of stops must be minimized.
In order to insure that the rapier heads are properly aligned for transfer it is necessary to limit the divergence of the heads when they come together. One way to limit divergence is to provide for stabilization of the rapiers while they travel in the shed. My copending application Ser. No. 686,651 filed May 14, 1976 of common ownership herewith, describes apparatus which utilize the warp shed sheets to provide stabilization. The instant invention provides an alternative way to limit the divergence and obtain proper alignment of the rapier heads when they come together for transfer.